Online charging is a process where charging information for network resource usage is collected concurrently with that resource usage, but where authorization for the resource usage is obtained by the network as a predicate to allowing the actual resource usage to occur or continue. For example, a subscriber attempts to connect to a data service through a wireless communication network and, according to online charging principles, a credit reservation is made against the subscriber account associated with the subscriber as part of the credit control that is performed before allowing the data session to be established. Further subsequent reservations may be made, as needed, to cover the costs associated with continuing the data session. Of course, the use of online charging is not limited to data services and covers event-based and session-based communications.
In a more detailed example of session-based online charging, a network subscriber requests a communication service and an “Online Charging System” or OCS initially reserves some amount of credit from the involved subscriber account. This reservation equates to some usage quota for the service, which may be expressed in terms of the resource units by which the service is metered—e.g., minutes, bytes, etc. The service is initiated based on the quota and, when the quota is used up, the session may be terminated or further credit reservations may be made against the subscriber account, assuming that sufficient credit remains available in the account to authorize additional quotas. Once the session is terminated, information about the number of resource units consumed is reported to the OCS in a final charging event.
In the context of networks based on the “Third Generation Partnership Project” or 3GPP specifications, the OCS includes an “Online Charging Function” or OCF that in turn includes distinct modules, namely a “Session Based Charging Function” or SBCF, and an “Event Based Charging Function” or EBCF. The SBCF is responsible for online charging of network/user sessions, e.g. voice calls, “Internet Protocol Connectivity Access Network” or IP CAN bearers, IP CAN sessions, and “IP Multimedia Subsystem” or IMS sessions. The EBCF performs event-based online charging, which is also referred to as “content charging”, in conjunction with any application server or service network element, including Session Initiation Protocol, “SIP”, application servers.
Example details regarding charging management, charging architectures and charging principles are readily available. In the above 3GPP context, see 3GPP TS 32.240 V12.6.0 (2014-12), “Technical Specification 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Telecommunication management; Charging management; Charging architecture and principles (Release 12)”.
There are a number of challenges related to online charging beyond the obvious need to reliably capture, track and charge chargeable events in the network. For example, a subscriber may be involved in multiple chargeable events involving different services. Thus, the credit reservations made against the subscriber account for initiating or continuing a given service should not be excessive, elsewise sufficient credit would not remain for authorizing other services. On the other hand, there is significant signaling associated with making credit control requests, providing corresponding credit control responses, and performing the associated account control needed to log the credit reservations against subscriber accounts. Consequently, credit reservations that are too small lead to undesirably frequent credit control transactions and higher signaling overhead.